Benchmark: equal vs assign vs defineProperty

Script Preparation code:

var a = 'a'

Tests:

equal
var b = {} b.a = a
assign
var b = {} Object.assign(b, { a })
defineProperty
var b = {} Object.defineProperty(b, 'a', { value: a })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
equal
assign
defineProperty

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36 Edg/115.0.1901.188

Browser/OS: Chrome 115 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
equal	27006778.0 Ops/sec
assign	7781065.0 Ops/sec
defineProperty	4464913.5 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

Measuring JavaScript performance is crucial for optimizing code, especially in modern web applications.

The provided benchmark measures the performance of three different ways to assign or create properties on an object:

1.  **`equal`**: This method uses the assignment operator (`=`) to set the value of `a` as a property of the `b` object. It's equivalent to doing `b.a = a`.

2.  **`assign`**: This method uses the `Object.assign()` method to assign the value of `a` as a property of the `b` object.

3.  **`defineProperty`**: This method uses the `Object.defineProperty()` method to define a new property called "a" on the `b` object, with its value set to `a`.

**Comparison**

Here's a brief comparison of these three approaches:

*   **`equal` and `assign` are very similar**, as both create a new property on the object. The main difference is that `Object.assign()` is a method call, while assignment operator (`=`) is an operator.
*   **`defineProperty`** is different from the other two methods because it requires an explicit definition of the property's metadata (e.g., its name and whether it's writable or configurable). This can be beneficial for performance in some cases.

**Pros and Cons**

Here are some pros and cons for each approach:

*   **`equal`**: Pros: simple, widely supported. Cons: might lead to unnecessary object creation if the property value is large.
*   **`assign`**: Pros: efficient, works well with arrays and objects. Cons: requires a method call, which can be slower than operator-based assignments.
*   **`defineProperty`**: Pros: allows for fine-grained control over property metadata, which can improve performance in some cases. Cons: more complex syntax, might be less familiar to some developers.

**Library Usage**

None of the test cases use a library explicitly. However, `Object.assign()` is a standard method that's part of the ECMAScript specification (ECMA-262). It was introduced in ECMAScript 2015 as a way to perform property assignment on objects.

**Special JavaScript Features or Syntax**

None of the test cases use any special JavaScript features or syntax. They all rely on standard language constructs for object creation and assignment.

**Other Alternatives**

In general, when creating new properties on an object in JavaScript, you can also consider other approaches:

*   **Using a constructor**: If you need to create objects with a specific set of properties, you can use a constructor function. This approach can be more efficient than using `Object.assign()` or assignment operators.
*   **Using `Object.create()` and `Object.defineProperty()`**: If you need to create an object that inherits from another object, but doesn't want to inherit all its properties, you can use `Object.create()` and `Object.defineProperty()`. This approach gives you more control over the object's prototype chain.

In conclusion, when it comes to creating or assigning properties on objects in JavaScript, there are several approaches to choose from. The best choice depends on your specific use case, performance requirements, and personal preference.

Related benchmarks:

equal vs assign vs defineProperty (version: 0)

Comparing performance of: equal vs assign vs defineProperty

Created: one year ago by: Registered User

Jump to the latest result

equal

assign

defineProperty

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):